Make-and-break device for periodic or cyclic application o fluid pressure



Dec. 18, 1956 H. 1 MCCOMBS, 1R 2,774,370

MAKE-AND BREAK DEVICE FOR PERIODIC 0R cYcLrc APPLICATION 0F FLUID PRESSURE Filed May 1o, 1952 ATTORNEY MAKE-AND-BREAK DEVICE FOR PERIGDIC OR CYCLIC APPLICATIGN F FLUID PRESSURE Howard L. McCombs, Jr., South Bend, Ind., assigner to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application May 10, 1952, Serial No. 287,200

8 Claims. (Cl. 137-103) The instant invention had its inception in the need for a simple and convenient yet eiective means for working or exercising the air and fuel diaphragms and associated parts used for controlling the regulator valve of Stromberg injection carburetors. When such a carburetor is overhauled after a given number of hours of ight service and re-assembled and reset it is customary to work or exercise the moving parts to ensure against sluggish action and sticking or in other words, to stabilize the carburetor and minimize any tendency toward subsequent drift, viz., departure from the final calibration and adjustment to specications. Thus, the diaphragms may lose some of their exibility during overhaul and there may be burrs or rough spots on replaced parts. Hence the carburetor is run in before it is again put in ight service. Such working may also be advisable or necessary in any carburetor whether after assembly and adjustment at the factory or following a certain period of non-use at the factory or in the field. However, the device of the present invention has been found to be exceptionally convenient for use in the eld where the more elaborate equipment and experienced personnel usually found at the factory is not available. Obviously, such a device is not restricted in service to exercising or working carburetors but may be used wherever the application of periodic or cycle pulsations of fluid pressure may be necessary or desirable.

An object of the invention, therefore, is to provide a device for producing periodic or intermittent uid pressure pulsations at any desired point of application. Y

Another object is to provide a device of the type specified which is simple and compact in construction and capable of being used by unskilled personnel.

Another object is to provide a device for producing fluid pressure pulsations wherein the amplitude and frequency of the pulsations may be varied as desired simply by substituting diiferent relative sizes of restrictions or bleeds.

The foregoing and other objects and advantages will become apparent in view of the following description taken in conjunction with the drawing, wherein the sole figure illustrates in sectional schematic a device in accordance with the invention.

Referring to the drawing, a casing or hollow housing is generally indicated at 10; it is made up of a main body section 11 and an upper section or cap 12, having a ange f 13, which is secured to the base 11 by means of screws 14. A diaphragm 15 has'its peripheral edge clampingly engaged between the iiange 13 and adjacent wall of the base 11, said diaphragm forming a movable wall between atmospheric chamber 16 and suction chamber 17. A valve 18, shown in a form of a at disc of suitable material, is secured to the central portion of the diaphragm 15 by means of a screw bolt 19 and bushings 20 and 21. The valve 18 serves as an intermittent closure for suction chamber 22. VThe chamber 16 is vented to the atmosphere at 23.

A suitable source of suction or vacuum, not shown, is connected by means of air line 24 and restriction orbleed 2S to the chamber 22; and leading from said chamber i' Yuited States Patent O Patented Dec. 18, 1956 through restriction or bleed 26 is another air line 27, which is adapted for connection to the point of intermittent or periodic application of suction, here chamber B of a carburetor regulator section. An air line 27 Acommunicates the said chamber B with suction chamber 17 through a restriction or bleed 2S.

As heretofore noted, the illustrated embodiment of the invention is shown as applying periodic pulsations to the regulator section 30 of a Stromberg carburetor. That portion of the regulator shown comprises a regulator valve, the stem of which is indicated at 31, which is connected by means of a series of coacting bushings 32 to the central portion of a series of diaphragms 33, 34 and 35. The diaphragm 33 is commonly known as the air diaphragm, and it forms a movable wall between impact pressure chamber A and venturi suction chamber B; whereas the diaphragm 34 is commonly known as the fuel diaphragm and forms a movable wall between metered fuel chamber C and unmetered fuel chamber D. When the carburetor is functioning on an engine, an air differential pressure is set up across the diaphragm 33, which varies as a function of the velocity of the air owing to the engine, and a fuel differential pressure is set up across the diaphragm 34, which varies as a function of the rate of ow of fuel to the engine. These respective dilferentials oppose one another and act through the diaphragms to so position the regular valve as to maintain a given fuel head across the carburetor metering restrictions, not shown, for a given rate of mass air ow.

Operation The effective or exposed area of the valve 18 is less than that of the diaphragm 15. For example, valve 18 may have an effective area of say one-third of that of diaphragm 15. When suction or P1 pressure is applied through the air line 24, the P2 pressure in chamber 22 drops, and this low pressure or suction is communicated through bleed 26 and air line 27 to the regulator chamber B and thence by way of air line 27 and restriction or bleed 28 to chamber 17. T he pressures in air lines 27 and 27' and chamber 17 are indicated, respectively, as P3, P4 and P5 pressures. The low pressure P2 or suction force in chamber V2.2 tends to hold valve 18 to its seat. However, since the diaphragm 15 is of greater eifective area than that of the valve 18, when the suction in chamber 17 has increased to a certain point, the force P5 applied to the diaphragm 15 becomes sufficient to overcome the resisting froce or suction P2 holding the valve to its seat, whereupon the valve snaps open and atmospheric pressure in chamber 16 is communicated to chamber 22 and in turn builds up in conduit 27, regulator chamber B, conduit 27 and chamber 17 and as it builds up in the latter chamber, the gravity effect or weight of the valve assembly causes the valve again to seat and the cycle is re- Y peated. Optionally, a spring 36 mayv bev provided to ensure seating of the valve, particularly where a vertical position is not convenient.

tions may be varied within limits at a given value of applied suction. ForY example, a decrease in the size of restriction'26 at a given size of restriction 28 Vwill result in a cycle of less frequency and amplitude, since it will require a longer period of time for the suction force P5 to build up in chamber 17 and hence there will be a longer dwell of valve 18. .'By decreasing the size of restriction 28 at a given size of restriction 26, the amplitude of each cycle is increased and the frequency decreased.v

A change in size of restriction-25 has only a minor effectY on cycle amplitude and frequency.

The frequency or cyclic rate can also be varied `by varying the relative areas of diaphragm 15 and valve 18, it Y 

